GRAND TRAVERSE COUNTY, MI -- A 12-year-old girl was struck by an alleged drunken driver as she walked with her mother Thursday night, then the mother was struck by a second vehicle as she knelt to help her daughter in the roadway, police say.

The young girl was airlifted from Munson Hospital in Traverse City to Helen DeVos Children's Hospital in Grand Rapids. Her injuries were considered non life-threatening, police say, but her condition Friday morning was not clear. Authorities did not identify those involved.

The extent of the mother's injuries was not clear, but they were also not believed to be life-threatening, Michigan State Police Sgt. Shawn Wise told MLive/The Grand Rapids Press.

State troopers from the Cadillac post were called to the crash scene in the area of Cook Road and Old M-72 Highway near Williamsburg around 9:15 p.m. Aug. 21. The location is in Whitewater Township, between Traverse City and the Torch Lake area.

Investigators believe the mother and daughter were walking south on the northbound shoulder of Cook Road when the first crash, involving the 12-year-old, occurred. The section of rural road is straight, though the two were lit only by a hand-held light carried by the mother. The speed limit is 55 mph.

As the mother knelt to assist her daughter, she was struck by a second vehicle. The two were in a traffic lane after the first crash, Wise said.

Police say the first driver was arrested for operating while intoxicated causing serious injury. The second driver was not intoxicated and was not found to be at fault, troopers say.

Wise declined to identify those involved, saying additional information would be released to media later Friday.